The amount of fuel required for a spaceship to get to Mars depends on the weight of the vehicle as well as the flight path used. India's unmanned Mars orbiter, for example, weighs 3,000 pounds, and it carries 200 tons of fuel in addition to its solar panels.
The method of travel also affects how much fuel a rocket requires to reach Mars. A rocket that accelerates halfway to Mars and then decelerates until it arrives has a shorter travel time but requires an impractical amount of fuel. Other theoretical fuel options, aside from nuclear power, also include antimatter, of which only 10 milligrams is required for a rocket from Earth to reach Mars in 45 days.